Investigation of buffer-cyclodextrin systems

Equilibrium constants for the formation of inclusion compounds of 3-hydroxy -2-naphthoic acid with beta-cyclodextrin were determined in aqueous solutio ns, in the absence and presence of buffers, by the steady-state fluorescenc e Benesi-Hildebrand method. Almost all the buffers that are usually used ha ve been tested and they are found to have an influence on the formation con stants. We suggest that buffers should not be used in aqueous solutions of cyclodextrins unless the experimental error is unacceptable. Furthermore, w e obtained the inclusion compound formation constants (K-salt) of beta-CD w ith some buffer components by using a fluorescence competitive inhibition t echnique. NaClO4, KClO4, KCl, KHC8H4O4, KH2C6H5O7 and NaHC4H4O6 can form 1: 1 inclusion complexes with beta-cyclodextrin (K-salt > 0) while KF, K2SO4, NaH2PO4, NaAc, Na2HPO4 and NaHCO3 cannot (K-salt < 0).